The village of Sanzeno was the scene of the spiritual struggle waged by three young missionaries who had been commissioned by Bishop Vescvo Vigilio to convert this region, which had originally been inhabited by the Rhaetians and then the Romans. In 397 Martyrius, Sisinius and Alexander were killed and burnt at the stake. First a chapel and later a basilica were built at the sacrificial site. Building work was completed in 1542 by Prince Bishop Vescovo Cristoforo Madruzzo. The Romanesque bell tower, made of stone, dates back to before 1000. Inside, with three naves, the chapel belonging to the earlier church, a small memorial chapel dedicated to the three saints and the shrine which houses their remains.